My question is should I use the OTW (oil to water) cooler in the radiator or not. I'm really hoping Mark Kovalsky chimes in on this one.

Last week my truck started to get the torque converter shudder. So I started to monitor the trans temp via the Torque APP and I've noticed it runs pretty hot while cruising down the freeway (not towing 65mph) between 200-210*. I did the tranny flush last night fallowing the write up instructions by Mark (Castrol Mercon V 20 qts). Glad I did, the fluid was looking pretty dark and my oil cooler bypass valve seems to be failing, or I have a blockage in the cooling system. Ordering a new CBV today or tomorrow reguardless to rule it out. Test drove it last night and still ran hot 205* or so. I fallowed the lines and found that the cooler supply line goes into an aftermarket plate & fin cooler, then into the oem OTA (Oil To Air) cooler and back into the rear of the trans, completely bypassing the OTW cooler in the radiator. The cooler supply line is hot to the touch and the return line back to the trans is much cooler so I know at least SOME fluid is making it's way through the cooling system. I adjusted the height of the aux cooler to get more air flow and it now hovers between 190-197* (cruising 65mph). And i'm still getting the shudder once the temp reaches 170* or higher but only once in a while from 1st to 2nd shift.

I want to do what is the best cooling set up and plum the cooler lines into the radiator as well if you guys recomend it. Yes I know 6.0 cooler is king, but for now I'm focusing on pluming order first. I have to replace the supply line if this is the case since the guy who owned the truck before me hacked it all up when he installed the aftermarket cooler. FTE best forum hands down.

 

I'm sure Mark will be able to help you more than I can. In the meantime, here are a few old threads I started somewhat on topic:

https://www.ford-trucks.com/forums/1...ew-cooler.html

https://www.ford-trucks.com/forums/1...ghts-mark.html

 

Thanks for the feedback. In one of those threads, mark explains the in radiator trans cooler is on the "cool" side of the radiator and is made of coiled tubing. I wasn't aware of that and it sounds efficiant enough to run reguardless of my set up. Well i guess that will settle it then. I'll make preperations to plum it back into service.

I wonder how I can flush that cooler in the radiator before I put it back in service. The fittings do not have plugs in them so they've been open to the atmosphere for who know how long. I'd imagine it's nasty in there by now. I obviously don't want to flush it with water. Thoughts??

 

I don't know of an effective way to flush it. If it just had been opened, maybe. But being open for who knows how long I wouldn't use it. I do highly recommend a radiator cooler, just not the one in your truck.

 

Thanks Mark for your input. If you highly recomend it then I'm on that path. I started this thread to find out the how effective the radiator cooler is on these vehicles. It seems like a no brainer.

 

Here is a photo that shows what the cooler looks like inside the lower tank of the radiator. It is a stacked plate design.

My '99 didn't come with the OTW cooler. I simply added a small stacked plate supplemental cooler to the stock 7.3 unit and it's performed very well. My truck is a 4x4 so I get to use low range when backing up a heavy trailer. In my opinion, the OTW cooler is very useful when towing at very low speeds or in reverse. If I ever need to replace the radiator in my '99 then the new part will automatically come with the OTW cooler so I'll probably use it (as long as the total trans fluid flow is not restricted too much...) When airflow is sufficient, a supplemental OTA cooler is all you really need. Here is the unit that I've been running for the last 8 or 9 years.
transmissioncoolers.us: Tru-Cool LPD, thick cooler & standard installation kit
Total combined weight while towing is around 25,500 lbs. Ambient temps are usually in the 110 degree range.....trans fluid temp usually runs about 60 degrees over ambient when unloaded and 80 degrees over ambient when towing (mountain terrain).

 

The auxiliary cooler installed on my truck is almost identical to the tru-cool in your link. Makes me wonder why its running so hot. Thank you for the info, you have a very nice setup.

 

The stacked plate design is very efficient, much better then fin and tube models. I think you may have more then just a cooling issue with your trans. Something may be generating a lot of heat in there. It might be wise to take it to a reputable shop and have them check it out.

 

Point taken on the tube & fin cooler inefficiancy and taking it to a reputable shop for inspection.
I noticed something when I drove it again last night. The TC seems to be locking & unlocking every 4-5 seconds, only in overdrive though. That can't be normal, right? The tach fluctuates 200 rpm or so when it's doing this. When I turn OD off on the fwy at 65mph it doesn't seem to happen and the temp begins to drop little by little. I dont feel or hear any rpm change while cruising in 3rd and when I let off the throttle the TC stays engaged. I didn't have time to look for any loose wire connections, but it now has my full attention.

 

Not normal.
Did you recently install LED tail lights by any chance?
Are any of the incandescent bulbs burned out?
(it's a long shot but something easy to check so I thought I'd ask....here is the TSB)

 

No I don't have LED's installed in the tail lights at all. I've seen the TSB your referring to. I'll check for burnt out bulbs in all 3 tail lights after work, but as far as I know they are all working well. I've done some recent searching here on FTE & google and cannot find anything pertaining to the torque converter intermittently locking in overdrive. Where are the electrical connectors located? I know there is a violet/yellow wire controlling TC lockup located in the grey 16-pin connector on the fender well. Is there any other wire connectors to inspect for this? Or perhaps any diagnosing I can try?

I don't know if it is directly related but my cruise control will not turn on (no CC light in gauge cluster when CC "on" button is pressed). Also, my truck will not enter the KOEO self test by holding the CC ON button & turning ignition to ON.

 

Have you had the Cruise Control recall done yet?
CC being disabled and the self test not running could be related. Do you have a way to pull codes and view live data?

The solenoid pack in the transmission is on the right side, it's a bear to get to due to the exhaust system down there. If you can connect a scan tool and monitor the TC lock solenoid along with TC slip actual then you can determine if the TC is unlocking and if it's being commanded to do so. That will point you to a wiring or possible mechanical issue.

 

This leads me to suspect the brake light switch is the cause of both the cruise and torque converter problems.

 

I wasn't aware of a cruise control recall, I'll look into it at the dealership. I had the brake switch recall done 8 months ago. I can read the data you mentioned with my buddy's snap on scan gauge probably next weekend. The CC has not worked since I've owned the truck which is only about a year or so. I replaced the clock spring which fixed a few problems I was having but not the CC.

 

Checked all tail lights, they're working fine. Had to tow a 16ft flat bed unloaded 20 miles (I had no choice but to tow) trans temp reached 217. Pulled over held high idle in neutral to cool down. Towed only in 3rd, couldn't pass 50mph. Read T/C slip via torque app on my phone, not very accurate but noticed t/c not locking up. Anything over 1/4 throttle and it slipped 500rpm and temp would rise.

I have no choice but to take it to a shop.